John Edwards' endorsement of Barack Obama came late in the campaign, but the timing seemed as fitting as his opening tribute to Hillary Clinton. It has been a tough campaign, with two strong candidates, both of whom are highly qualified for the presidency.

Maybe Edwards wanted to let the remaining voters have their say before he jumped in. Or maybe he himself was having a hard time making up his mind. Now, he was saying, it's time to wrap this thing up and focus on the general election.

Edwards' endorsement isn't likely to influence many voters in the last handful of primaries. But it may sway some superdelegates. And it's one more emotional defeat for Clinton.

Edwards could be a huge help as Obama struggles to connect to Clinton's base: working class whites, older women, and older voters in general. His endorsement speech contained the fire and emotion about working-class issues that Obama hasn't been able produce so far.

Edwards' was a classy speech, just what Obama needed right now. And you've got to wonder: was it also a try-out for the vice-presidential nomination?